ELECTRO-MECHANICAL APPARATUS INSTALLED IN A RAILROAD CAR FOR MEASURING AND PROCESSING DATA RELATED TO TRAIN OPERATION AND TRACK CONDITIONS, INCLUDING TRACK GEOMETRY, TRAIN SPEED, TRAIN DISTANCE TRAVELED, AND TRACK STRESS, STRAIN AND VIBRATION ENCOUNTERED BY A TRAIN DURING ITS RUN; DIGITAL FILTERS; DIGITAL CASSETTE RECORDERS; STRUCTURAL CURVE DETECTORS; PROFILOMETERS; AND CAPACITIVE SENSORS